The present invention concerns the cleaning of shields in a physical vapor deposition chamber.
In physical vapor deposition (PVD) processes a target material, for example tungsten, is bombarded by a gas, for example argon. Material from the target is dislodged and sputters onto a wafer.
A PVD chamber generally includes shields in the area immediately around a wafer. The shields prevent excess material sputtering from the target from contaminating the remainder of the PVD chamber.
The build-up of excess material on the shields eventually results in flaking. At this point it is usually necessary to service the PVD chamber by replacing the shield. If shield replacement needs to be done at approximately the same time as target replacement, the service to the shield may be performed without too much inconvenience. However, if the shield needs to be replaced much more often than the target, this can result in extra down-time of the system which can seriously impair production throughput.
Several methods have been tried to reduce flaking and thereby lengthen the time between shield replacement. For example, some shields have been designed to have a specific expansion coefficient. Additionally, the surface of shields has been treated, for example, by sandblasting. Adhesion layers also have been laid down to prevent flaking. Finally, shield design may be simplified to facilitate easy replacement.